OTHER ANSWERS

Sorry to hear about the Paypal error. If you have not already, please see our tutorial on <a href="http://www.inmotionhosting.com/support/edu/prestashop-15/314-install-configure-paypal" target=-"_blank">Installing and configuring the Paypal module in PrestaShop 1.5</a>. This error is an Authentication/Authorization Failed error code. PayPal says,

"This error can be caused by an incorrect API username, an incorrect API password, or an invalid API signature. Make sure that all three of these values are correct. For your security, PayPal does not report exactly which of these three values might be in error. "

Double check your PayPal credentials to see if you have the correct PayPal information or t if the connection is actually sending the data (ie, that your <a href="http://www.inmotionhosting.com/support/domain-names/dns-nameserver-changes/updating-your-domains-nameservers">domain points</a> to us and that you are testing on the correct server and not locally).